TORONTO The mother of two small boys strangled by a 100-pound pythonin their sleep earlier this week in Canada had posted photos on Facebook last year of the boys playing in and cleaning her neighbor's snake enclosure.

Mandy Trecartin's Facebook page has hundreds of photos of her sons, including a few showing Noah Barthe, 4, and Connor Barthe, 6, happily scrubbing the glass enclosure, which she identified as an anaconda habitat. It was not clear whether the enclosure is the one that held the python.

Preliminary results from autopsies performed on the boys show they died from asphyxiation, officials said Wednesday. The shocked community planned a vigil Wednesday.

The snake, an African rock python, apparently escaped from its enclosure, slithered through a ventilation system and fell through the ceiling into the room where the young boys were sleeping, authorities said. They had been visiting the apartment of a friend whose father owned an exotic pet store on the floor below.

A snake expert said it was possible that the python was spooked and simply clung to whatever it landed on.

Authorities on Wednesday planned to remove other animals from the pet shop, though Royal Canadian Mounted Police Sgt. Alain Tremblay said the 4.3-meter (14-foot) python was being kept inside the apartment. Police are treating the deaths in Campbellton, New Brunswick, as a criminal investigation.

Tremblay said the snake was housed in a large glass enclosure that reached the ceiling of the apartment and escaped through a small hole in the ceiling connected to the ventilation system. He said the snake made its way through the ventilation system, the pipe collapsed and the snake fell.

The friend of the boys was sleeping in another room and was unharmed.

The pet store owner, Jean-Claude Savoie, has told a television station that he didn't hear a sound and discovered the "horrific scene" when he went into his living room on Monday morning.

Police stand in front of Reptile Ocean pet store in New Brunswick, Canada on Aug. 5, 2013, after two young boys were strangled as they slept by a python that escaped the store and apparently slithered through the ventilation system into the apartment above. Their tricycles can be seen at bottom left.

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Steve Benteau, a spokesman for the provincial Natural Resources Department, said no permit was issued for an African rock python. The department said the snake is generally only permitted in accredited zoos, unless there is a special permit.

Police said the snake was killed by a veterinarian. It was sent for a necropsy to confirm the type of snake and help understand what may have caused it to attack.

Reptile expert Bry Loyst, curator of the Indian River Reptile Zoo in Ontario, said the New Brunswick government has asked him for help in removing animals from the pet store and taking them to accredited zoos elsewhere in the country.

Loyst said police told him it wasn't the first time that the python had escaped. Royal Canadian Mounted Police Const. Julie Rogers-Marsh said she could not confirm that because she had not heard that.

Paul Goulet, founder and co-owner of Little Ray's Reptile Zoo in Ottawa, said snakes don't recognize humans as a source of food, but if the children smelled like animals, it could explain an attack.

"If a snake sees an animal moving, giving off heat and smells like a goat, what is it? It's a goat," Goulet said.

Family spokesman Dave Rose, the boys' great-uncle, said the brothers had spent Monday at Savoie's family farm and played with llamas, goats, horses and dogs and cats before staying over at the apartment.

Snake expert John Kendrick, a manager at the Reptile Store in Hamilton, Ontario, said that if pythons are startled, they can grab something for stability, and it's possible that the python was just holding on to what it landed on, Kendrick said.

"Once they are in constricting mode, any part of their body that is touching something that moves, they'll wrap it," he said. "I've seen snakes with two different prey items at the same time, one with the back of the body and one with the front. It could have been an incident like that."